Robinson Helicopter Company R44 II N163RK accident near Marble Falls, Texas

Probable cause

A total loss of engine power due to fuel contamination from an unknown source.

NTSB analysis

The pilot of the helicopter was conducting an aerial observation flight when, about 250 ft above ground level (agl) and about 50 knots indicated airspeed, the engine lost total power. The pilot entered an autorotation, negotiated a powerline, and landed on a hill. During the landing, the helicopter rocked forward and aft, striking and substantially damaging the lower vertical stabilizer.

Postaccident examination revealed water and a reddish-colored polyamide substance in the main fuel tank, auxiliary fuel tank, electric fuel pump, and gascolator. Further examination of the polyamide was inconclusive for a single known substance. The pilot reported that during the three-day mission, he refueled the helicopter at three different airports as well as his own personal fuel supply. Postaccident examination of the owner’s personal fuel supply and each of the airport’s fuel delivery systems did not reveal the presence of contamination. The circumstances of the accident are consistent with a total loss of engine power due to fuel contamination; however, the source of the contamination could not be determined based on the available information.

Text from the NTSB. Open the NTSB docket for WPR23LA263 for the full record.